Gram quantities of highly purified human thrombin preparations are being produced to enable investigations on the structure, enzymic specificity, and physiologic functions of human alpha-thrombin and derivative forms Beta- and gamma-thrombins. Ongoing projects in this laboratory are: (1) continual production of human alpha-thrombin, gamma-thrombin, and by-products (e.g., plasminogen, prothyrombin complex, prothrombin activation fragment fractions); (2) further refinement of methods and assay techniques (e.g., improved methods for increasing thrombin storage stability); (3) adaptation of methods for preparing thrombins from other species and comparing them with human thrombins (e.g., bovine and porcine thrombins); (4) further studies on thermal and autolytic decomposition of alpha-thrombin (e.g., effects of various cations and anions); and (5) further studies on the properties and specificities of human alpha- vs. Beta- and gamma-thrombin and conversion of alpha-thrombin to derivative forms (e.g., autolysis vs. tryptic conversion vs. other proteases). Major collaborative studies include: (1) identification of the cleavage sites in forming Beta- and gamma-thrombins (D.A. Walz, Detroit, MI); (2) exo-site affinity labeling of alpha- and derivative thrombins (D.H. Bing, Boston, MA); (3) crystallographic studies on alpha-thrombin (R.M. Stroud, Pasadena, CA); (4) examination of conformational states of thrombin forms (L.J. Berliner, Columbus, OH); (5) studies on the specificity of thrombin forms with chromogenetic peptide substrates (N.U. Bang, Indianapolis, IN); and (6) studies of thrombin reactions with platelets (T.C. Detwiler, Brooklyn, NY; T.S. Zimmerman, La Jolla, CA), plasma protease inhibitors (R.D. Feinman, Brooklyn, NY; P.G. Harpel, New York, NY; N.U. Bang), and complement and related systems (A. E. Hugli, La Jolla, CA; V.H. Donaldson, Cincinnati, OH; T.B. Taylor, Oklahoma City, OK; D.H. Bing). Other studies using our preparations range from those on the induction of mitogenesis in tissue cultures to the in vivo disposition and effects of thrombin in animal model systems.